KR20110076461A - A tubular braid and composite hollow fiber membrane using the same - Google Patents

Abstract

PURPOSE: Tubular braid and composite hollow fiber membrane using the same are provided to secure the stability of complete products by obtaining uniform polymer resin thin film layer. CONSTITUTION: Tubular braid(1) is braided yarn composed of multifilament and is based on one or more selected from a group including polyethylene terephtalate and nylon. False twist yarn is composed of 10 to 200 mono filaments. The width of the false twist yarn is between 5 and 500 denier. The width of the mono filaments is between 0.3 and 50 denier. The total width of the tubular braid is between 100 and 800 denier.

Description

Tubular knitted fabric and composite hollow fiber membrane using the same {A tubular braid and Composite Hollow Fiber Membrane using the same}

Embodiments of the present invention are directed to hollow fiber membranes that can be used in water treatment, and more particularly to composite hollow fiber membranes.

In general, it is well known that water treatment using a separation membrane is a purification technique using a selective permeation mechanism of a material. At this time, the water treatment using the membrane, that is, the separation of contaminated water is not only economical in terms of energy saving, facility simplification, and operation efficiency compared to the distillation method used in the conventional chemical treatment, A wide range of research and practical use has been made, ranging from laboratory scale to various industrial sectors. Such membranes may be morphologically listed as flat membranes, tubular membranes, hollow fiber membranes, etc. The flat membranes have high pollution resistance and are widely applied as wastewater treatment technologies, but are difficult to install economically due to their low density per unit volume. Hollow fiber membrane is morphologically shaped in the form of a yarn and can pack a lot of membranes per unit volume, thereby increasing throughput. However, hollow fiber membranes are often easily cut off during operation due to low mechanical strength, and in particular, these disadvantages act as a deterrent to securing high quality water. The composite hollow fiber membrane used as the separator must exhibit excellent permeability and at the same time exhibit excellent mechanical strength. Recently, the composite hollow fiber membrane is applied to a water treatment process in the form of an immersion type module, and the immersion type module is composed of an essential process for cleaning through aeration, and is operated by repeated cycles of operation / rest in order to minimize membrane contamination. In this case, friction, physical shock, and continuous operation and repetition of the hollow fiber membranes due to the aeration may cause the film to deviate from the support of the membrane and its own peeling at the interface between the module and the membrane. In order to apply such hollow fiber membranes to various water treatment fields, various characteristics such as excellent permeability, excellent mechanical strength, high filtration reliability, high peel strength, low dope penetration, and high stiffness are required.

Embodiments of the present invention is composed of a twisted yarn to provide a tubular knitted fabric excellent in adhesion and peel strength with the polymer resin film layer.

Embodiments of the present invention provide a composite hollow fiber membrane having improved mechanical strength by using the tubular knitted fabric.

One aspect of the present invention relates to a tubular knitted fabric knitted from false twisted multifilament knitted with fineness 5 to 500 denier, 10 to 200 filaments.

Another aspect of the present invention is a hollow knitted fabric reinforced composite hollow fiber membrane comprising a tubular knitted fabric knitted with false twisted multifilament knitted with fineness 5 to 500 denier, 10 to 200 filaments and a polymer resin thin film layer coated on the surface of the tubular knitted fabric. It is about.

Since the false twist yarn constituting the tubular knitted fabric according to the embodiments of the present invention forms a stretchy and unsmooth surface due to its twisting property, the dope solution is easily penetrated into the knitted fabric, thereby increasing the bonding force of the polymer resin thin film layer and the knitted fabric. The durability and reliability of the composite hollow fiber membrane produced by this can be improved. In addition, when the external tension is lost, since it has a restoring force, a uniform polymer resin thin film layer can be obtained, thereby securing stability of the product.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a composite hollow fiber membrane according to an embodiment of the present invention.

As shown in Figure 1, the composite hollow fiber membrane according to an embodiment of the present invention is a tubular braid (1), a polymeric resin thin film (2) coated on the surface of the tubular knitted fabric (1) as a reinforcing material and treatment It consists of a hollow part 3 for receiving the material. The tubular knitted fabric 1 is recombined with twisted yarn multifilament consisting of 5 to 500 deniers and 10 to 200 pillars of fineness to knit 100 to 800 deniers in total fineness.

Since the twisted yarn has the property of twisting, the knitted fabric has elasticity in the longitudinal direction and the polymer dope solution penetrates into the stretched knitted fabric by the tension applied in the longitudinal direction of the knitted fabric in the section where the polymer dope solution is applied to the tubular knitted fabric (1). It becomes easy. As a result, the bonding strength of the polymer resin thin film layer 2 and the knitted fabric may be increased to improve the peel strength of the manufactured composite hollow fiber membrane.

In addition, the unsmooth surface of the combustible yarn not only strengthens the adhesive strength with the polymer resin thin film layer, but also has a restoring force so that the hollow of the tubular knitted fabric 1 can be removed by sufficiently removing the polymer dope solution after penetrating into the tubular knitted fabric 1. Roundness can be improved.

To this end, the false twisted multifilament is preferably made by combining a plurality of monofilament having a fineness of 0.3 to 50 denier.

50 degrees of monofilament fineness When the denier is exceeded, the fiber becomes thicker, which makes it difficult to manufacture the tubular knitted fabric 1 having a high hollow roundness, and when the fineness is less than 0.3 denier, the tubular knitted fabric 1 acts as a resistance during the water permeation process to reduce water permeability. .

The false twisted multifilament configured as described above is formed by combining 10 to 200 monofilaments in terms of peel strength, dope penetration control, and economic efficiency, and the fineness of the formed multifilament may be in the range of 5 to 500 denier. It is preferable that the total fineness of the yarn (yarn) which consists of such a twisted yarn multifilament is 100-800 denier, More preferably, it is 250-600 denier.

If the total fineness of the yarn is less than 100 denier, the production speed is lowered, and if the total fineness of the yarn exceeds 800 denier, the outer diameter of the tubular knitted fabric (1) is expanded to reduce the density per unit volume.

The material of the tubular knitted fabric 1 according to one embodiment of the present invention may be a polyethylene terephthalate (PET), nylon (Nylon), etc. containing a polar group, but is not necessarily limited thereto. Polyethylene, polypropylene, etc., which are composed of non-polar molecular chains, have poor adhesion with the coating layer, while polyester-based and polyamide-based materials containing polar groups have excellent interfacial adhesion with the coating layer.

According to one embodiment of the invention, the polymer resin thin film (2) is coated on the surface of the tubular knitted fabric (1) to form a composite hollow fiber membrane, the polymer resin thin film (2) is the mechanical strength of the composite hollow fiber membrane, the water permeability of the membrane And filtration reliability. The polymer resin thin film 2 has a mechanical strength such that the polymer resin thin film 2 itself is lower than the tubular knitted fabric 1, so that the polymer resin thin film 2 itself does not peel or break, and complements the tensile strength and the pressure resistance of the composite hollow fiber membrane.

According to one embodiment of the present invention, since the tubular knitted fabric 1 has a relatively large void compared to the polymer resin thin film 2, the filtrate passing through the polymeric resin thin film 2 has a tubular knitted fabric having a large void ( Passes 1) without great resistance. That is, the water permeability of the filtrate is affected by the polymer resin thin film 2 having small pores, and the water permeability of the entire composite hollow fiber membrane is determined by the micropore structure and porosity of the polymer resin thin film 2.

The micropore structure and porosity of the polymer resin thin film 2 is determined according to the difference in thermodynamic stability according to the composition of the dope. In more detail, when the solvent or additives constituting the dope solution strongly interact with the polymer, a sponge-like structure is formed due to the 'demixing delay effect' between the polymer and the coagulation bath solution. As the interaction with the polymer becomes weaker, the 'mixing effect' proceeds rapidly to form a finger-like structure. The sponge structure is advantageous over the finger structure in terms of mechanical strength, but disadvantageous in terms of water permeability. The reason is that the sponge structure has a strong hydraulic resistance compared to the finger structure. On the other hand, the surface pore size distributed on the surface shows an important function for imparting reliability of the filtration characteristics. That is, the formation of the surface pore having the same distribution excludes particles of a certain size or more to impart stability of the water quality in the water treatment process.

According to one embodiment of the present invention, the polymer resin thin film (2) forms a sponge structure up to 50 ~ 190 ㎛ in the lower layer and the finger structure up to 0.1 ~ 10 ㎛ in the lower layer in order to simultaneously express mechanical strength, water transmission rate, filtration reliability To minimize the distribution of surface porosity. Micropores having a pore size of 0.01 to 1 μm may be formed in the surface layer, and micropores having a pore size of 0.01 to 10 μm may be formed in the inner layer. In addition, when the diameter of the micropores formed in the inner layer of the composite hollow fiber membrane gradually increases toward the center direction to increase the asymmetry, the water permeability can be enhanced.

Next, the polymer resin thin film 2 is applied to the tubular knitted fabric 1 and undergoes a solidification process. As the organic solvent is released during the solidification process, a pore is formed therein. At this time, since the surface layer of the polymer resin thin film 2 has a faster solidification rate than the inner layer, the pore size of the surface layer is formed relatively smaller than the pore size of the inner layer.

In one embodiment of the present invention, the thickness of the polymer resin thin film (2) is preferably in the range of 10 to 200㎛, when the thickness of the polymer resin thin film (2) is less than 10㎛ when the mechanical strength is lower, when larger than 200㎛ There is a drop in water permeability. The distance that the polymer resin thin film 2 penetrates into the tubular knitted fabric 1 is preferably in the range of 10 to 30% of the thickness of the tubular knitted fabric 1 (that is, the difference between the outer diameter and the inner diameter of the tubular knitted fabric 1). This is because the mechanical strength drops when the tubular knit fabric 1 is smaller than 10% and the water permeability decreases when the tubular knit fabric 1 is larger than 30%.

The polymer resin thin film 2 according to an embodiment of the present invention is formed by coating a surface of the tubular knitted fabric 1 with a spinning dope composed of a polymer resin, an organic solvent, and an additive polyvinylpyrrolidone and a hydrophilic compound. .

In the process of manufacturing a composite hollow fiber membrane according to an embodiment of the present invention, the tubular knitted fabric (1) passes through the tubular knitted fabric (1) to the center of the double tubular nozzle and flows the spinning dope into the surface of the tubular knitted fabric (1). Coating the spin dope on the surface of the substrate). Subsequently, the spinning dope may be discharged into the air outside the nozzle, coagulated with an external coagulation liquid, and then washed with water and dried.

In one embodiment of the present invention, the spinning dope is prepared by dissolving a polymer resin, an additive polyvinylpyrrolidone, and a hydrophilic compound in an organic solvent. The preferred content range is 10 to 50% by weight of the polymer resin, polyvinylpyrrolidone and 1 to 30% by weight of the hydrophilic compound, and 20 to 89% by weight of the organic solvent.

The polymer resin used in one embodiment of the present invention is polysulfone resin, polyethersulfone resin, sulfonated polysulfone resin, polyvinylidene fluoride (PVDF) resin, polyacrylonitrile (PAN) resin, polyimide resin , At least one selected from the group consisting of polyamideimide resins, and polyesterimide resins can be used. At this time, at least one selected from the group consisting of dimethylacetamide and dimethylformamide may be used as the organic solvent. As the surface pore-forming agent, at least one selected from the group consisting of water or polypyrrolidone-based compounds may be used. If the polypyrrolidone compound is less than 1% does not form a uniform surface pore, if the polypyrrolidone compound is 30% or more, the mechanical strength is lowered by the brittleness of the thin film.

Hereinafter, after the composite hollow fiber membranes are prepared through Examples and Comparative Examples, the properties of the composite hollow fiber membranes prepared according to the Examples of the present invention will be described by measuring physical properties thereof. The listed examples are for ease of understanding and are not intended to limit the invention.

Example  1: Preparation of Composite Hollow Fiber Membrane

50 denier twisted yarn multifilament 6 strands composed of 36 filaments of polyethylene terephthalate (PET) monofilament having 1.4 denier were filamented so that the total fineness of one yarn was 300 denier. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm.

As a dope solution, a composition composed of 17% polyvinylidene fluoride (PVDF), 10% polyvinylpyrrolidone, and 73% dimethyl acrylamide was sufficiently dissolved at 40 ° C, and then degased to remove the gas generated. Placed at room temperature. The prepared dope solution was supplied to a double tubular nozzle and the dope solution was coated on the outside of the tubular knitted fabric by passing through the tubular knitted fabric prepared in the center. At this time, the thickness of the coating was 0.2mm. The knitted fabric which passed the air gap (5 cm) was coagulated in an external coagulation bath at 30 ° C. Thereafter, in order to remove residual solvents and additives, the mixture was post-treated in a hydrothermal apparatus at 60 ° C. for 1 day, immersed in 20 wt% alcohol solution for 2 hours, and then dried in a dryer at 40 ° C. for 24 hours to obtain a composite hollow fiber membrane.

The composite hollow fiber membrane exhibited a peel strength of 1.50 Mpa, a water permeability of 550 LMH, and maintained a hollow source.

Example  2: Preparation of Composite Hollow Fiber Membrane

Six strands of 50 denier twisted yarn multifilament consisting of 100 filaments of polyethylene terephthalate (PET) monofilament having a fineness of 0.5 denier were spun together so that the total fineness of one yarn was 300 denier. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm. Formation of the coating layer was performed according to the same preparation and process as in Example 1.

The composite hollow fiber membrane exhibited characteristics of peel strength of 0.90 MPa and water transmittance of 485 LMH. Compared to Example 1, the number of fineness of the fineness of Denia is lower, so that the space for the dope solution to penetrate into the knitted fabric has a lower peeling strength, and the dope solution that does not penetrate into the knitted fabric thickens the polymer resin thin film layer. Was somewhat lower.

Example  3: Preparation of Composite Hollow Fiber Membrane

Six strands of 50 denier twisted yarn multifilament consisting of 10 filaments of polyethylene terephthalate (PET) monofilament having 5 deniers of fineness were spliced to give a total fineness of 300 denier per yarn. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm. Formation of the coating layer was performed according to the same preparation and process as in Example 1.

The composite hollow fiber membrane exhibited characteristics of peel strength of 2.10 MPa and water permeability of 610 LMH. Compared to Example 1, the denier number of fineness is high, and the coarse twisted yarn filament is applied, so that the dope solution easily penetrates into the knit fabric, the peel strength is high, and the polymer resin thin film layer is thinned, thereby improving water permeability.

Comparative example  1: Preparation of Composite Hollow Fiber Membrane

Six 50 strands of stretched multifilament of 50 denier yarns consisting of 36 strands of PET monofilament having a fineness of 1.4 denier were spliced to obtain a total fineness of 300 denier per yarn. Then, using the 26 yarns prepared to prepare a tubular knitted fabric woven so that the outer diameter is 1.9 mm. The subsequent process obtained the composite hollow fiber membrane by the process and conditions similar to Example 1.

The composite hollow fiber membrane exhibited a low peel strength of 0.72 MPa. This is thought to be because the dope solution is not easy to penetrate into the tubular knitted fabric.

Comparative example  2: Preparation of Composite Hollow Fiber Membrane

Six strands of stretched multifilament of 50 deniers consisting of 10 filaments of polyethylene terephthalate (PET) monofilament having 5 deniers of fineness were spliced to give a total fineness of 300 denier per yarn. Thereafter, using the 26 strands of yarn, a tubular knitted fabric having an outer diameter of 1.9 mm was prepared. Formation of the coating layer was performed according to the same preparation and process as in Example 1.

The prepared composite hollow fiber membrane had a water permeability of 492 LMH and a peel strength of 0.91 MPa.

As shown in the examples and comparative examples, the reinforcement hollow fiber membrane using the combustible yarn was improved in peel strength compared to the hollow fiber membrane composed of the conventional yarn.

Peel strength

The load at the moment of peeling of the polymer resin thin film from the tubular knitted fabric was measured using a tensile tester, and the peel strength was calculated by dividing this by the area (㎡) to which the shear force was applied. Specific measurement conditions are shown in Table 1 below.

TABLE 1

Peel strength is defined as shear strength per unit area applied to the coated polymer resin thin film when the specimen is tensioned, and the area (m ² ) to which shear force is applied is π × outer diameter of the composite hollow fiber membrane (m) × Calculated by the adhesion length (m). The calculation is as follows.

Peel strength (Pa) = load at yield point (kg) / area under shear (m ² )

Permeability  Measure

A compact pressure module with a membrane area of 0.0057 m ² was fabricated and placed in a device with a pressure gauge. The interlayer differential pressure was kept constant at 100 kPa and RO water of 24 ± 1 ° C. was supplied to measure the water permeation rate for 2 minutes. The unit of permeation amount is LMH (L / m ² × h).

Although the present invention has been described in detail with reference to preferred embodiments of the present invention, it will be apparent to those skilled in the art that the present invention may be variously changed or modified without departing from the spirit and scope of the present invention. Modifications and variations are also to be construed as being included in the scope of protection of the present invention.

The following drawings illustrate one embodiment of the present invention, and together with the detailed description of the present invention serve to assist in understanding the present invention, the present invention should not be construed as limited to the matters set forth in these drawings.

1 is a cross-sectional view of a composite hollow fiber membrane according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: tubular knitted fabric 2: polymer resin thin film

3: hollow part

Claims (11)

Tubular knitted fabric knitted from yarn composed of false twisted multifilament. The tubular knitted fabric of claim 1, wherein the twisted yarn multifilament is formed by combining 10 to 200 monofilaments, and has a fineness of 5 to 500 denier.           3. The tubular knitted fabric of claim 2, wherein the monofilament has a fineness of 0.3 to 50 denier. 　 The tubular knitted fabric of claim 1, wherein the total fineness of the tubular knitted fabric is between 100 and 800 denier. 　 The tubular knitted fabric of claim 1, wherein the tubular knitted fabric is made of one or more selected from the group consisting of polyethylene terephthalate and nylon. A composite hollow fiber membrane comprising a tubular knitted fabric knitted from false twisted multifilament composed of fineness 5 to 500 denier and 10 to 200 filaments and a polymer resin thin film coated on the surface of the tubular knitted fabric . The method of claim 6, wherein the polymer resin thin film layer forms a sponge-like structure from 50 to 190 ㎛ in the lower layer and 0.1 to 10 ㎛ in the upper layer to form a finger-like structure (finger-like structure) Composite hollow fiber membrane. The composite hollow fiber membrane of claim 6, wherein the polymer resin thin film layer comprises a surface layer having a pore size of 0.01 to 1 μm and an inner layer having a pore size of 0.01 to 10 μm. The composite hollow fiber membrane according to claim 6, wherein the polymer resin thin film layer has a thickness of 10 to 200 µm. 　 The composite hollow fiber membrane according to claim 6, wherein the total fineness of the tubular knitted fabric is 100 to 800 denier. 　 7. The composite hollow fiber membrane according to claim 6, wherein the tubular knitted fabric is made of at least one selected from the group consisting of polyethylene terephthalate and nylon.

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